This investigation has been designed to develop and refine methods for modifying psychosocial factors and behaviors which have been found to be associated with coronary heart disease (CHD), and to develop and refine instruments to demonstrate the nature and magnitude of such changes. Psychological and behavioral indices, including compliance, will be measured. The project will be implemented among 100 post-myocardial infarction patients who are assigned randomly to two pyschological treatment groups (group therapy and relaxation response therapy) and to a control group, which receives no psychological treatment. Medical treatments will be administered independently of psychological intervention. Patients will be in the treatment programs for one year and will be followed at three-month intervals for 1 1/2 years, on the average. Experimental and control patients will be followed simultaneously. In addition to data directly associated with psychosocial and behavioral change, including compliance, the design permits collection of a variety of relevant data, including cardiac outcome event, other medical/biological variables, and demographic and socio-economic measures. The data will be analyzed in such a way as to provide indications for future research. More sophisticated hypotheses and treatment information which the study will yield should lead to clinical trials whose primary outcome criterion is the reduction, by means of psychological intervention, of the incidence of fatal and non-fatal cardiac events. Two cooperating hospitals will participate in the project in order to expedite intake and to help appraise and anticipate the problems involved in a multicenter clinical trial such as may result from the findings of this study.